Filters of the type used for filtering particulate matter from fluid sometimes include a filter housing having an inlet for receiving the fluid with entrained particulate matter, and an outlet for delivering the filtered fluid to a device needing fluid that is free of particulate matter. For example, a filter may be provided at the air inlet of an engine or an air compressor to remove dust, water, or other particulate matter that could cause damage to the engine or compressor if it were not removed from the air entering the engine or compressor.
In such filters, the particulate matter is typically removed by a filter element that is installed within the filter housing in such a manner that the fluid must flow through a filter element, including a filter pack of porous filter material, which removes the particulate matter from the fluid. Over time, the filter pack of the filter element becomes plugged or coated with particulate matter, necessitating removal and replacement of the filter element in order for the filter to continue in its function of supplying particulate-free fluid at the outlet of the housing.
In order to facilitate removal and replacement of the filter element, it is known to configure the filter housing to include a generally tubular wall section thereof, and provide a seal member mounted on the filter element that seals the juncture between an inner surface of the tubular wall section and the filter element, when the filter element is inserted into the housing, so that the fluid cannot bypass the filter element while flowing through the housing. Prior approaches to providing such sealing arrangement are disclosed in U.S. Pat. No. 6,190,432 to Gieseke et al., and in U.S. Pat. No. 6,517,598 B2 to Anderson et al.
Further, as shown in FIG. 9, filter apparatuses 710 of the type used for filtering particulate matter from fluid sometimes include a filter housing 712 having an inlet 714 for receiving the fluid with entrained particulate matter, and an outlet 716 for delivering the filtered fluid to a device needing fluid that is free of particulate matter. For example, a filter may be provided at the air inlet of an engine or an air compressor to remove dust, water, or other particulate matter that could cause damage to the engine or compressor if it were not removed from the air entering the engine or compressor.
In such filters 710, the particulate matter is typically removed by a primary filter element 718 that is installed within the filter housing 712 in such a manner that the fluid must flow through the primary filter element 718, in traveling from the inlet 714 to the outlet 716 of the filter 710. The filter element 718 includes a filter pack 720 of porous filter material, which removes the particulate matter from the fluid. Over time, the filter pack 720 of the primary filter element 718 becomes plugged or coated with particulate matter, necessitating removal and replacement of the primary filter element 718, in order for the filter 710 to continue in its function of supplying particulate-free fluid at the outlet 716 of the filter 710.
In order to facilitate removal and replacement of the primary filter element 718, it is known to configure the filter housing 712 to include a generally tubular wall 724 thereof, and to provide a seal member 742, mounted on the primary filter element 718, for sealing the juncture between an inner surface 726 of the tubular wall 724 and the filter element 718, when the primary filter element 718 is inserted into the housing 712, so that the fluid cannot bypass the primary filter element 718 while flowing through the housing 712.
Such filter apparatuses also sometimes include a secondary filter 727, inserted into the housing 712 downstream from the primary element 718. The secondary filter 727 is used as a safety filter, in case the primary filter 718 should come apart in service. Where the direction of airflow through the primary filter 718 is downward, as shown in FIG. 9, the secondary filter 727 also provides a means for catching any particulate matter that might otherwise fall from the primary filter element 718 into the outlet 716 of the housing 712, when the primary filter element 718 is replaced. Typically, the secondary filter element 727 is not replaced as frequently as the primary filter element 718.
In one commonly used prior filter apparatus 710, as shown in FIG. 9, the tubular wall 724 of the housing 712 is stepped to form first 728, second 730 and third 732 tubular sections of the housing 712, sequentially arranged along a longitudinal axis 734 of the filter housing 712, and having progressively decreasing cross-sectional areas. The inner surface 726 of the filter housing 712 defines a cavity 736 extending along the axis 734, with the inlet 714 at one axial end of the cavity 736 and the outlet 716 at the opposite axial end of the cavity 736. The first tubular section 728 extends from the inlet 714. The third tubular section 732 is disposed adjacent the outlet 716, and the second tubular section 730 connects the first and second tubular sections 728, 732. U.S. Pat. No. 6,517,598 to Anderson et al., illustrates a filter apparatus 710 of the type depicted in FIG. 9.
The secondary filter element 727 is inserted into the third tubular section 732, and seals against the inner surface 726 of the housing 712. The secondary filter 727 typically includes a filter material 729 attached to a rigid frame 731. The upstream side of the frame 731 is configured to function as a handle which can be grasped during insertion and removal the secondary filter 727. U.S. Pat. No. 6,517,598 to Anderson et al. and U.S. Pat. No. 6,211,122 to Gieseke et al., disclose this type of secondary filter element. Where the housing has a large cross-section, it has also sometimes been the practice in the past to include a specially formed handle on the frame 731 of secondary filter 727, with the handle extending some distance upstream, between the primary and secondary filter elements 718, 727, as illustrated in U.S. Pat. No. 6,235,195 to Tokar.
The primary filter element 718 includes the filter media pack 720, a mounting flange 740 attached to the inlet end of the media pack 720, and a seal support frame 744, which includes an annular axial extension thereof that projects axially from the outlet end of the media pack 720, for supporting the seal 742. The seal 742 is configured to seal radially against the inner surface 726 of the second tubular section 730 of the housing 712.
The seal support frame 744 typically includes webs 746 extending completely across the outlet end of the media pack 720. These webs 746 are provided to resist pressure forces acting on the media pack 720, which could cause the center of the media pack 720 to bow outward in a downstream direction. It has heretofore been believed, by those having skill in the art, that such webs 746 extending completely across the outlet face of the media pack 720 were particularly necessary in media packs formed by coiling layers of convoluted filter material to form a so-called “fluted filter,” in order to prevent the center of the filter media pack 720 from telescoping in a downstream direction under maximum rated inlet fluid pressures. U.S. Pat. No. 6,190,432 to Gieseke et al. and U.S. Pat. No. 6,610,177 to Tsay et al., disclose filter packs having seals attached to axially extending annular portions of a seal support frame.
As illustrated at ‘A’ in FIG. 9, having the seal 742 mounted on an axially extending annular extension of the seal support frame 744, together with the space occupied by the webs 746 at the outlet end of the filter pack 720, and the portions of the frame 731 of the secondary filter element 727 disposed between the primary and secondary filters 718, 727, undesirably consumes a significant portion of the volume in the cavity 736 of the housing 712 between the primary and secondary filters 718, 727. This is particularly true where the secondary filter element 727 includes a handle, as disclosed by Tokar.
It is desirable, therefore, to provide an improved filter element, and filter apparatus in a form which better utilizes the volume inside of the cavity of the filter housing, and particularly in a form which better utilizes the volume between the primary and secondary filter elements in a filter apparatus, of the type described above, which includes both a primary and a secondary filter element.